Supported Client Protocols

Squid supports the following incoming protocol request types, when the proxy requests are sent in HTTP format:

• File Transfer Protocol (FTP)
• Gopher
• HyperText Transfer Protocol (HTTP)
• Secure Socket Layer (SSL)
• Wide Area Information Server (WAIS)

Inter-cache and Management Protocols

• Cache Digests: Used to retrieve an index of objects in another cache's store
• HyperText Transfer Protocol (HTTP): Used for retrieving copies of objects from other caches
• Hyper Text Caching Protocol (HTCP):
• Internet Cache Protocol (ICP): Used to find out if a specific object is in another cache's store
• Simple Network Management Protocol (SNMP): Can be used to retrieve information about your cache

Inter-cache Communication Protocols

Squid enables you to share data between caches. Just as there is a benefit to connecting individual PCs to a network, and this network to the Internet, there is also an advantage to linking your cache to other people's networks of caches.

User Base: The larger your user base, the more objects requested, the higher the chances of an object being requested twice. In order to increase your hit rate, add more clients.

Reduced Load: If you have a large network, one cache might be unable to handle all incoming requests. Rather than having to continuously upgrade one machine, it makes sense to divide the load between multiple servers. This reduces an individual server’s load, while increasing the overall number of queries your cache system can handle.

Squid implements inter-cache protocols very efficiently, through ICP multi-cast queries and cache digests, which allow for large networks of caches (hierarchies).

 

Disk Space: If you load-balance between multiple caches, avoid duplication of data. Duplicated objects reduce the quantity of objects in the overall store, which reduces your chances of a hit. Using the Cache Array Routing Protocol (CARP) or other inter-cache communication protocols reduces duplication.

 
Raw bandwidth is not the only issue affecting the efficiency and speed of your cache system. Choosing the right hardware and software also presents its own challenges.